The California-based First Amendment Coalition says the LAPD may have snared innocents when tracking the targets of investigations

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A California free speech advocate has raised questions about the Los Angeles Police Department's use of a controversial technology that tracks an individual’s location via cellphones.

The technology, known as Stingray, connects to all cellphones within range of its tower, letting police know who is passing by and at what time.

The Los Angeles Police Department used the technology 21 times in a four-month period in 2012, capturing information not only about the people they were tracking, but “potentially hundreds of innocent persons who happen to be in the vicinity of the devices,” Peter Scheer, executive director of the San Rafael-based First Amendment Coalition, said on the organization's website this weekend.

The records show that the LAPD did obtain search warrants before using the technology in its cases. But Scheer said that its use raised privacy concerns for motorists and others whose data might be captured along with the targets of police investigations.

He also criticized what he said was the police agency’s increasing use of Stingray.

“The Stingray devices were reportedly acquired by the LAPD, using a federal Homeland Security grant, for counter-terrorism investigations following the 911 terrorist attacks,” Scheer wrote on the coalition’s website. “However, the records obtained by FAC indicate the tracking technology is now used for more routine criminal investigations.”

LAPD officials were not immediately available for comment about Scheer's allegations. This story will be updated to reflect the agency's response.